U.S. Pat. No. 6,935,116 B1 discloses a gas turbine combustion system for reducing polluting emissions such as NOx and CO, while being able to provide stable combustion at lower load conditions. The combustion system contains a casing having a center axis, which is in fluid communication with the engine compressor, and an end cover fixed to the casing. In the preferred embodiment, the end cover contains a plurality of first injectors arranged in a first array about the end cover and a plurality of second injectors arranged in a second array about the end cover, with the second array radially outward of the first array. Located proximate the end cover is a first swirler, also called swirl generator, having a plurality of passageways oriented generally perpendicular to the casing center axis for inducing a swirl generally radially inward to a first portion of the compressed air. Fuel, which is injected through the first and second injectors, mixes with the first portion of compressed air from the first swirler before entering a liner through a dome section. Additional fuel is also introduced to a second portion of compressed air through a plurality of third injectors located in a manifold of an aft injector assembly. The third injectors are divided into multiple circumferential sectors to allow for various fuels staging circumferentially around the aft injector assembly. To enhance mixing between fuel from the third injectors and second portion of compressed air, a second swirler is positioned adjacent the aft injector assembly for imparting a swirl to the second portion of compressed air. This fuel and air mixes in a second passage located between a first part of the liner and the dome prior to entering the liner and mixing with the fuel and first portion of compressed air from the first swirler region. Upon entering the liner, the pre-mixture from the second passage must undergo a complete reversal of flow direction that causes strong recirculation zones at the forward end of the liner. These recirculation zones help to increase combustor stability by providing a region where a portion of the hot combustion gases can be entrained and recirculate to provide continuous ignition to the incoming premixed fuel and compressed air. Fuel flow to each of the first, second, and third sets of injectors is controlled independently to allow for fuel staging throughout various load conditions to control NOx and CO emissions at each load set-ting.
U.S. Pat. No. 5,577,378 discloses a gas turbine group, comprising at least one compressor unit, a first combustion chamber for generating working gas, wherein the first combustion chamber connected to receive compressed air from the compressor unit. Furthermore, the first combustion chamber being an annular combustion chamber having a plurality of premixing premixed burners. A first turbine connected to receive working gas from the first combustion chamber. A second combustion chamber connected to receive exhausted working gas from the first turbine and deliver working gas to the second turbine. The second combustion chamber comprising an annular duct forming a combustion space extending in a flow direction from an outlet of the first turbine to an inlet of the second turbine; means for introducing fuel into the second combustion chamber for self-ignition of the fuel. A plurality of vortex generating elements mounted in the second combustion chamber upstream of the means for introducing fuel; and, a single rotor shaft supported by not more than two bearings, the at least one compressor unit, where-in first turbine and second turbine being connected on the rotor shaft, wherein the compressor unit consists of at least one compressor. The annular combustion chamber comprises a plurality of individual tubular units defining combustion spaces disposed circumferentially with respect to rotor shaft. The first turbine is configured for partially expanding the working gas so that working gas exhausted from the first turbine has a temperature sufficient for self ignition of a fuel in the second combustion chamber. The vortex generators in the second combustion chamber are shaped and positioned to each generate vortices in the flow. Accordingly, combustion systems of prior art, which utilise premixed burners according to the documents EP 0 321 809 A1 and/or EP 0 704 657 A1 are of silo or annular design type, wherein these documents forming integral parts of the present description.
One of those premixed burners consisting of hollow part-cone bodies making up a complete body, having tangential air inlet slots and feed channels for gaseous and liquid fuels, wherein in that the centre axes of the hollow part-cone bodies have a cone angle increasing in the direction of flow and run in the longitudinal direction at a mutual offset. A fuel nozzle, which fuel injection is located in the middle of the connecting line of the mutually offset centre axes of the part-cone bodies, is placed at the premixed burner head in the conical interior formed by the part-cone bodies.
An other premixed burner substantially consisting of a swirl generator, which substantially consisting of hollow part-cone bodies making up a complete body, having tangential air inlet slots and feed channels for gaseous and liquid fuels. The centre axes of the hollow part-cone bodies have a cone angle increasing in the direction of flow and run in the longitudinal direction at a mutual offset, wherein a fuel nozzle, which fuel injection is located in the middle of the connecting line of the mutually offset centre axes of the part-cone bodies, is placed at the premixed burner head in the conical interior formed by the part-cone bodies. A mixing path provided downstream of said swirl generator, wherein said mixing path comprises transaction ducts extending within a first part of the path in the flow direction for transfer of a flow formed in said swirl generator into the cross-section of flow of said mixing path, that joins downstream of said transition ducts.
Compared to an annular type of design, the state of art does not offer un-confined a higher service-ability. The plurality of premixed burners distributed in circumferential direction does not give possibility to adjust an optimal combustion for each premixed burner load and type of fuel, due to operative interference of adjacent premixed burners.
EP 1 055 879 A1 discloses a combustion chamber assembly which comprises a can-combustor which is a tubular combustion chamber (see column 8, line 35). Along the axis of the tubular combustion chamber a burner arrangement consisting of a fuel injector and a mixing duct is provided which supplies a fuel-air mixture within a first combustion zone inside the can-combustor. Along the sidewall of the can-combustor two further arrangements are provided, each of which injects a fuel-air mixture into the can-combustor. This document does not contain any passages in which the term “premix burner” is disclosed. The combustion zones are significantly spaced apart from the secondary and tertiary fuel and air mixing ducts. So the presumption is obvious that the combustor disclosed in this document is a so called diffusion burner arrangement.
EP 1 752 709 A2 discloses reheat combustion in a gas turbine system. The main aspect refers to a reheat device which is arranged downstream to the first turbine into which a further fuel stream is injected which enhance the temperature increase of the partially expanded working gas stream. This document is silent concerning the shape and embodiment of the combustor Further there is no disclosure concerning the use of a pre-mix burner.